Problem: $\left(-9x + 1\right)\left(4x - 2\right) = \ ?$
Explanation: $= -9x \cdot \left(4x - 2\right) + 1 \cdot \left(4x - 2\right)$ $= \left( -9x \cdot 4x \right) + \left( -9x \cdot -2 \right) + \left( 1 \cdot 4x \right) + \left( 1 \cdot -2 \right)$ $= -36x^2 + \left( -9x \cdot -2 \right) + \left( 1 \cdot 4x \right) + \left( 1 \cdot -2 \right)$ $= -36x^2 + \left( 18x + 4x \right) + \left( 1 \cdot -2 \right)$ $= -36x^2 + 22x + \left( 1 \cdot -2 \right)$ $= -36x^2 + 22x - 2$